While industries are developing rapidly, the needs for reflecting layers also grow in all aspects including mobile phones, MP3, displays, lamp housing, lamp reflectors, etc. Usually, the form of reflecting layers varies from flat ones such as sheets and plates to complicated forms by the press process. As materials, silver, aluminum, copper, rhodium, platinum are used, which have high reflectance. In spite of excellent reflecting properties, such metal materials usually have low chemical stability and are difficult to be processed to surface state with high illuminance and great reflectance. They are also heavy and disadvantageous in terms of price, so there are some problems to process metal materials directly to reflecting layers.
Japanese Laid-Open Patent Publication No. PYUNG2005-157296 discloses the preparation method of white reflecting layers by powder coating using titanium dioxide (TiO2). There are similar methods that form white reflecting layers by coating paints including pigments of metallic oxide such as silane oxide, titanium dioxide, magnesium oxide, and barium oxide directly on metal plates, but they have some disadvantages of low reflectance and poor weather resistance.
Also, when materials such as silver (Ag) or chromium (Cr) are used, reflecting layers having advanced-quality surface gloss and high reflectance can be obtained. However, there are often defective proportions during production and plating costs too much, which could lead to air pollution and waste water due to discharge of noxious substance.
On the other hand, Japanese Laid-Open Patent Publication No. PYUNG2002-129259 discloses the preparation method of high reflecting layers by vacuum evaporation using silver as its main component. After vacuum evaporation using high reflecting metals including silver (Ag), aluminum (Al), nickel (Ni), rhodium (Rh) on the surface of flexible materials such as PET, reflecting layers can be made through laminating on the support. However, there are a few disadvantages that vacuum evaporation needs a high vacuum chamber and it may restrict the form and size of the material and make coating thickness not uniform, and the equipment costs a lot, too.